Sheet material for extraction, extraction filter, and extraction bag

ABSTRACT

A sheet material for extraction with excellent transparency and extraction properties, is less likely to cause powder leakage, and has high modulus and excellent machine adaptability; an extraction filter; and an extraction bag. The sheet material having a first layer of a spunbonded nonwoven fabric formed from polyester-based fibers having an average diameter of 18 to 28 μm, the fabric having a basis weight of 8 to 19 g/m 2 ; and a second layer of a meltblown nonwoven fabric formed from polyester-based fibers having an average diameter of 16 to 28 μm, the fabric having a basis weight of 2 to 8 g/m 2 , wherein the sum of the lengths of all fibers included in 1 cm 2  of the sheet material for extraction is 3.3 to 4.8 m, and the 3% modulus is 5.5 N or higher; and an extraction filter and an extraction bag formed by this sheet material for extraction.

TECHNICAL FIELD

The present invention relates to a sheet material for extraction capableof extracting a beverage or the like from an extraction material, suchas tea leaves, herb, or powdered coffee, and to an extraction filter andan extraction bag (hereinafter, an extraction filter and an extractionbag will be collectively referred to as “filter and the like forextraction”) produced by subjecting the sheet material for extraction toprocessing such as cutting and adhesion. More particularly, the presentinvention relates to the sheet material for extraction that hasexcellent transparency and extraction properties, is less likely tocause powder leakage, and has high machine adaptability in theproduction of a filter and the like for extraction, and to a filter forextraction and the like having excellent handleability and made from thesheet material for extraction.

BACKGROUND ART

Conventionally, the sheet material for extraction as materials forfilters and bags are used for extraction of beverages such as black tea,green tea, herbs, and coffee; liquid food products such as soup;medicines such as Chinese herbal medicines, or bathing agents. Manynonwoven fabrics formed from synthetic resins have been employed fromthe viewpoint of increasing the rate of extraction, reducing the cost,and the like. In recent years, there is a tendency that more emphasis isput on the beauty of the external appearance in the sheet material forextraction, such as a sense of transparency and a sense of glossiness.

Particularly, in a case where bags for extraction is filled withhigh-quality tea leaves having beautiful green color or various brightlycolored herbs as extraction materials, high transparency is required forthe sheet material for extraction as the material of the bags such thatthe beauty of brightly colored tea leaves and herbs can be visuallyrecognized through the sheet material for extraction.

In order to increase the transparency of the sheet material forextraction, for example, the fiber spacing may be widened by shorteningthe length of fibers included per unit area of the nonwoven fabric thatconstitutes the sheet material for extraction. In order to do so, thebasis weight of the nonwoven fabric may be lowered, and further thefiber diameter may be enlarged if the basis weight is the same.

Furthermore, when the fiber spacing is widened as such in the nonwovenfabric that constitutes the sheet material for extraction, the quantityof airflow is increased, and at the same time permeability to hot wateror water is also increased. Therefore, the rate of extraction isincreased, i.e., the extraction properties are enhanced.

However, when the fiber spacing is widened in the nonwoven fabric thatconstitutes the sheet material for extraction, and the extraction filteror the extraction bag is produced by such sheet material for extraction,“powder leakage” by which fine powder included in the extractionmaterial escapes through the fiber spacings is likely to occur. In acase where the powder leakage is severe, the appearance is deterioratedby contaminating the periphery or by leaking a large quantity of finepowder into the beverage or the like, causing a problem that the foodtaste is deteriorated.

Further, when the basis weight is made lower in the nonwoven fabric thatconstitutes the sheet material for extraction in order to enhancetransparency or extraction properties in the sheet material forextraction, the modulus (tensile stress) is decreased in the sheetmaterial for extraction. Then, when a large tensile force is applied tothe sheet material for extraction at the time of processing the sheetmaterial for extraction by a machine or the like, the sheet material forextraction undergoes deformation such as stretching and is not restoredto its original shape, which may cause the occurrence of defectiveproducts, i.e., which may causes a problem that the machine adaptabilityis deteriorated for the sheet material for extraction.

For example, when the extraction filter and the like is produced by theelongated sheet material for extraction, a large tensile force may beapplied instantaneously upon the initiation of the machine operation oremergency shutdown of the machine. When the modulus is low in the sheetmaterial for extraction, a portion of the sheet material for extractionmay be stretched and deformed, and thus defective products may beproduced.

Japanese Patent Application Publication No.2015-74838 (PatentLiterature 1) discloses a technology for a food filter formed from apolyester long fiber nonwoven fabric produced by a spun-bonding method.This nonwoven fabric has high transparency, low boiling water shrinkage,high dimensional stability, and excellent extraction properties.

However, since this food filter is formed from a single layer of thespunbonded nonwoven fabric formed from relatively thick fibers having anaverage fiber diameter of 15 to 40 μm (see claim 1 of Patent Literature1), the powder leakage tends to occur. Further, no description is givenin relation to the increase in the modulus for enhancing the machineadaptability, and this point of view is not taken into consideration.

Japanese Patent No. 3939326 (Patent Literature 2) discloses a technologyfor a teabag produced from a sheet material having a multilayerstructure formed from a nonwoven fabric produced by a spun-bondingmethod. The teabag has high transparency and is less likely to causepowder leakage.

However, since the nonwoven fabric constructing this teabag has a lowquantity of airflow (Frazier method JIS-L-1906) such as 140 to 280cc/cm³/sec (see Examples 1 to 6 of Patent Literature 2), the nonwovenfabric possesses insufficient extraction properties. Furthermore, thereis no description on the increase in the modulus for enhancing themachine adaptability, and this point of view is not taken intoconsideration.

Japanese Patent No. 4944545 (Patent Literature 3) discloses a technologyfor a food filter and its bag body each having a three-layer structure.These are less likely to cause powder leakage and have improved heatsealability and extraction properties.

However, this food filter is produced by interposing a meltblownnonwoven fabric having an average fiber diameter of 1 to 7μm between afirst layer and a third layer each formed from a spunbonded nonwovenfabric, and by thermally compressing the assembly.

Thus, since the average fiber diameter is very fine in the meltblownnonwoven fabric, the nonwoven fabric may have low transparency.Furthermore, there is no description on the increase in the modulus forenhancing the machine adaptability, and this point of view is not takeninto consideration.

CITATION LIST Patent Liteature

Patent Literature 1: Japanese Patent Application PublicationNo.2015-74838

Patent Literature 2: Japanese Patent No. 3939326

Patent Literature 3: Japanese Patent No. 4944545

SUMMARY OF INVENTION Technical Problem

The invention was achieved in view of the problems described above, andan object of the invention is to provide a sheet material forextraction, an extraction filter, and an extraction bag each havingexcellent transparency and extraction properties, being less likely tocause powder leakage, and having high modulus and excellent machineadaptability,.

Solution to Problem

Above problems are solved as follows.

[1] A sheet material for extraction includes a first layer including aspunbonded nonwoven fabric formed from polyester-based fibers having anaverage fiber diameter of 18 to 28 μm and a basis weight of 8 to 19g/m²; and a second layer including a meltblown nonwoven fabric formedfrom polyester-based fibers having an average fiber diameter of 16 to 28μm and a basis weight of 2 to 8 g/m², wherein the sheet material forextraction has a sum of the lengths of all fibers included in 1 cm² ofthe sheet material for extraction of 3.3 to 4.8 m and a 3% modulus of5.5 N or higher.

[2] The sheet material for extraction described in item [1], wherein thesheet material for extraction has a transparency of 40% or higher, aquantity of airflow of 400 cc/cm³/sec or greater, and a powder leakagerate of 10% or less.

[3] An extraction filter comprising the sheet material for extractiondescribed in item [1] or [2], wherein the extraction filter is formed bysuperposing the sheet material for extraction with the second layerbeing disposed on the inner side, and adhering the sheet material forextraction at predetermined sites.

[4] An extraction bag comprising the sheet material for extractiondescribed in item [1] or [2], wherein the extraction bag is formed bysuperposing the sheet material for extraction with the second layerbeing disposed on the inner side, and adhering the sheet material forextraction at predetermined sites to form a bag body with which anextraction material has been filled.

Advantageous Effects of Invention

With regard to the sheet material for extraction formed by the nonwovenfabric, when the basis weight of the nonwoven fabric is made small, orthe average fiber diameter is made large compared with nonwoven fabricshaving the same basis weight, the length of fibers becomes shorter in aunit area of the nonwoven fabric, and the fiber spacing is enlarged,thereby increasing light transmissibility and the quantity of airflow.Accordingly, the transparency and extraction properties of the sheetmaterial for extraction can be enhanced.

However, when the fiber spacing is enlarged in the nonwoven fabric, apowder leakage problem, in which fine powder included in the extractionmaterial leaks out through the fiber spacing and thus contaminates thesurroundings or is incorporated into a beverage or the like, is likelyto occur.

As such, since the enhancement of transparency and extraction propertiesand the reduction of powder leakage are contradictory to each other inthe sheet material for extraction, generally a compatibility of the twoat the same time is difficult to be achieved.

Furthermore, when the basis weight is made small in the nonwoven fabricin order to increase transparency and extraction properties of the sheetmaterial for extraction formed by the nonwoven fabric, the modulus(tensile stress) tends to become smaller in the sheet material forextraction. When the modulus becomes smaller in the sheet material forextraction, it is difficult for the sheet for extraction to be restoredto its original shape when the sheet for extraction is subjected toexternal force and is deformed. Therefore, defective products are likelyto be produced during production or processing.

In order to increase the modulus of the sheet material for extraction,for example, increasing the basis weight is desirable in the meltblownnonwoven fabric; however, in that case, the transparency and extractionproperties may be deteriorated in the sheet material for extraction.

As a result of a thorough investigation of the inventors of theinvention, with regard to a sheet material for extraction having aspunbonded nonwoven fabric layer (first layer) and a meltblown nonwovenfabric layer (second layer) each of layers being formed frompolyester-based fibers, the sum of the lengths of the fibersconstituting the first layer and the fibers constituting the secondlayer is regulated to be within a predetermined range in a unit area ofthe sheet material for extraction. Further, the 3% modulus of the sheetmaterial for extraction is regulated to a predetermined value orgreater, while the average fiber diameters and the basis weight of thefibers constituting the respective layers are respectively regulated tobe within a predetermined range. The inventors found that suchconfiguration can realize both the enhancement of transparency andextraction properties and the reduction of powder leakage and canprevent the defective products from being generated during production orprocessing. Thus, the inventors completed the invention.

That is, regarding the sheet material for extraction according to theinvention of the above item [1], since the sheet material for extractioncomprises a first layer formed by a spunbonded nonwoven fabric formedfrom polyester-based fibers having an average fiber diameter of 18 to 28the spunbonded nonwoven fabric having a basis weight of 8 to 19 g/m²;and a second layer formed by a meltblown nonwoven fabric formed frompolyester-based fibers having an average fiber diameter of 16 to 28 themeltblown nonwoven fabric having a basis weight of 2 to 8 g/m², whereinthe sum of the lengths of all fibers included in 1 cm² is 3.3 to 4.8 min the sheet material for extraction, thereby providing an advantageouseffect that highly excellent transparency and extraction properties areobtained, and powder leakage is less likely to occur.

Furthermore, since the sheet material for extraction according to theinvention of the above item [1] has a 3% modulus (tensile stress) of 5.5N or higher, the sheet material for extraction has a property that evenwhen the sheet material for extraction is subjected to external forceand is temporarily deformed, the sheet material for extraction tends torestore its original shape.

Therefore, for example, even when the sheet material for extraction isinstantaneously subjected to a large tensile force and temporarilyundergoes deformation such as stretching upon the initiation of themachine operation or emergency shutdown of the machine while producingthe extraction filter and the like from the sheet material forextraction, the sheet material for extraction immediately restores itsoriginal shape, and thus damage or permanent deformation thereof cannoteasily occur. Therefore, such a sheet material for extraction providesadvantageous effects of having high machine adaptability owing to thehardly generation of defective products while the sheet material isprocessed by the machine.

Meanwhile, the 3% modulus is the stress generated, when the sheetmaterial for extraction attempts to restore the original length afterthe sheet material for extraction is stretched by 3% of the length ofthe sheet material. It can be said that as this stress is larger, therestorability to the original length is higher.

Regarding the sheet material for extraction according to the inventionof the above item [2], since the sheet material for extraction has atransparency of 40% or higher, the extraction material within theextraction bag can be clearly recognized from the outside of theextraction bag which encapsulates the extraction material and isproduced from such a sheet material for extraction. Therefore, thecommercial value can be significantly increased particularly for theextraction bag encapsulating tea leaves of beautiful green color orvarious brightly colored herbs as the extraction material.

Furthermore, regarding the sheet material for extraction according tothe invention of the above item [2], since the quantity of airflow is400 cc/cm³/sec or higher, passage of hot water or water is easy, and theextraction filter and the like made from such a sheet material forextraction are capable of extracting a beverage or the like through theextraction material in a short period of time. Thus, the sheet materialfor extraction provides an advantageous effect for providing excellentextraction properties.

Furthermore, regarding the sheet material for extraction according tothe invention of the above item [2], since the powder leakage rate is10% or less, the sheet material for extraction can make it difficult forfine powder included in the extraction material to leak out from theextraction bag which encapsulates the extraction material and is madefrom this sheet material for extraction. Accordingly, the sheet materialfor extraction provides an advantageous effect for avoiding thecontamination of the machine for producing the extraction bag by finepowder, and reducing the amount of interfusion of fine powder into anextracted beverage or the like, so that the appearance and flavor can beenhanced.

With regard to the extraction filter according to the invention of theabove item [3], since the extraction filter is formed by superposing thesheet material for extraction according to the invention of the aboveitem [1] or [2], with the second layer being disposed on the inner side,and adhering the sheet material for extraction at predetermined sites,the transparency and extraction properties are highly excellent, andpowder leakage is less likely to occur.

Regarding the extraction bag according to the invention of the aboveitem [4], since the extraction material is encapsulated in the bag bodyformed by superposing the sheet material for extraction according to theinvention of the above item [1] or [2], with the second layer beingdisposed on the inner side, and adhering the sheet material forextraction at predetermined sites, the extraction material inside thebag body can be easily recognized visually from the outside through thesheet material for extraction having high transparency, and at the sametime, the extraction bag has highly excellent extraction properties andis less likely to cause powder leakage.

Therefore, when tea leaves having beautiful green color or variousbrightly colored herbs as the extraction material are encapsulated insuch an extraction bag, the extraction bag having favorable appearanceand high commercial value can be obtained.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view illustrating an embodiment of an extractionfilter according to the invention; and

FIG. 2 is a perspective view illustrating an embodiment of an extractionbag according to the invention.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the invention will be described. Meanwhile,the invention is not intended to be limited to these embodiments.

Furthermore, in the invention, a numerical value range represented bythe expression “. . . to . . . ” means a range including the numericalvalues described before and after the description “. . . to . . . ” asthe lower limit and the upper limit.

A sheet material for extraction of the present embodiment is suitable asa material for an extraction filter used by inserting the extractionmaterial into the filter and pouring hot water, water, or the like fromabove to be filtered therethrough, such as an extraction filter ofpowdered coffee, which is used by mounting the extraction filter on afunnel-shaped dripper. Furthermore, the sheet material for extraction issuitable as a material for an extraction bag that is a bag bodyencapsulating an extraction material, which is used by being immersed inhot water, water, or the like, such as a teabag.

Here, the extraction material includes, in a broad sense, a beveragematerial, a food material, a pharmaceutical product, a quasi-drug, andthe like, from which components are extracted into hot water, water, oralcohol,. Examples include tea leaves such as green tea, black tea,roasted green tea, oolong tea, and du zhong tea; barley tea; floweringtea; powdered coffee; dried fish shavings such as dried bonito shavingsand dried smoked mackerel shavings; dried kelp for soup stock; driedsardines; Chinese herbal medicines; and bathing agents.

The sheet material for extraction of the present embodiment has a firstlayer formed by a spunbonded nonwoven fabric and a second layer formedby a meltblown nonwoven fabric laminated together, and these nonwovenfabrics are formed from polyester-based resin fibers.

Here, the polyester-based resin is a linear polyester, a copolymerpolyester, or the like and can employ, for example, polyethyleneterephthalate, polybutylene terephthalate, or a polyethyleneterephthalate/polyethylene isophthalate copolymer in which thepolymerization ratio of the acidic components, namely, terephthalicacid/isophthalic acid, has been adjusted to an appropriate range.Furthermore, the polyester-based resin can employ a product obtained bypolymerizing terephthalic acid as a main component with 5-sodiumsulfoisophthalate, 4-hydroxybenzoic acid, adipic acid,naphthalenedicarboxylic acid, phthalic acid, naphthalenecarboxylic acid,diethylene glycol, propylene glycol, 1,4-butanediol, pentaerythritol, orthe like at an appropriate ratio, instead of isophthalic acid.

Furthermore, in the polyester-based resin used for the sheet materialfor extraction, other conventionally used components can be added to theextent without impairing the effects of the invention. For example,additives can be added as appropriate such as impact modifiers asvarious elastomers, a nucleating agent, a coloration preventing agent, adelustering agent, an oxidation inhibitor, a heat-resistant agent, aplasticizer, a lubricating agent, a weather-resistant agent, a coloringagent, a pigment, or the like.

The form of the fibers of the respective nonwoven fabrics forming thefirst layer and the second layer of the sheet material for extraction ofthe present embodiment can employ a monofilament, a multifilament, acomposite fiber having a core-sheath structure combining two kinds ofresins, or the like. Furthermore, the cross-sectional shape of thesefibers is not necessarily required to be a circular shape, and the shapemay be various shapes such as an oval shape, a triangular shape, andother polygonal shapes, or may also be a hollow shape.

The spunbonded nonwoven fabric forming the first layer of the sheetmaterial for extraction is a nonwoven fabric formed from relatively longfibers produced by a “spun-bonding method”. Furthermore, generally, thespun-bonding method is a production method of heating and melting a rawmaterial resin, extruding the molten resin through a spinning nozzle,pulling and stretching this extrusion product by spraying air at highspeed thereto while cooling to form fibers, subsequently accumulatingthe fibers on a collector such as a conveyor to form a web, subsequentlyadjusting the thickness of the obtained web or subjecting the web to apartial thermal compression treatment, using a flat roll, an embossedroll, or the like, which has been heated or not heated as necessary.

Meanwhile, during the partial thermal compression treatment, forexample, the above-mentioned web may be passed through between a pair ofrolls composed of the embossed roll having an uneven surface structureand the flat roll having a smooth surface to form a thermally compressedpart uniformly dispersed over the entirety of the spunbonded nonwovenfabric. Meanwhile, the area ratio of the thermally compressed part(thermal compression area ratio) is preferably 5.0% to 30.0% withrespect to the entire area of the nonwoven fabric surface, and softeningof the resin at the time of the partial thermal compression treatmentcan be carried out by any arbitrary means such as heating by a heater orvibrating with ultrasonic waves.

The spunbonded nonwoven fabric forming the first layer has an averagefiber diameter of 18 to 28 When the average fiber diameter is largerthan 28 the fiber length per unit area becomes short in the spunbondednonwoven fabric, the fiber spacing becomes excessively wide, and thenpowder leakage tends to occur easily. Further, when the average fiberdiameter is smaller than 18 the fiber length per unit area becomes longin the spunbonded nonwoven fabric, the fiber spacing becomes excessivelynarrow, and transparency and extraction properties tend to deteriorate.

Meanwhile, the “average fiber diameter” is the average value of thethickness of the fibers constituting the nonwoven fabric. When thecross-sectional shape of the fibers is a circular shape, the averagefiber diameter is an average value of the diameter of the fibers. Whenthe cross-sectional shape of the fibers is other than a circular shape,the average fiber diameter is an average value of the diameterobtainable in the case of converting the cross-sectional shape to acircular shape having virtually the same area.

The spunbonded nonwoven fabric that forms the first layer has a basisweight of 8 to 19 g/m². When the basis weight is more than 19 g/m², thefiber length per unit area becomes long in the spunbonded nonwovenfabric, the fiber spacing becomes excessively narrow, and thentransparency and extraction properties tend to deteriorate. Further,when the basis weight is less than 8 g/m², the tensile strength becomessmaller due to the shortening of the fiber length per unit area in thespunbonded nonwoven fabric, and the sheet material for extraction tendsto be easily damaged.

Meanwhile, in the spunbonded nonwoven fabric forming the first layer, anonwoven fabric other than the spunbonded nonwoven fabric, e.g., anonwoven fabric produced by another spinning method, or another materialcan be incorporated to the extent without impairing the effects of theinvention. The mixing ratio of such other nonwoven fabric or the like ispreferably approximately 10% or less with respect to the spunbondednonwoven fabric.

Next, the second layer of the sheet material for extraction of thepresent embodiment is formed by the meltblown nonwoven fabric. Themeltblown nonwoven fabric is a nonwoven fabric produced by a“melt-blowing method”. Generally, the melt-blowing method is aproduction method of heating and melting a raw material resin, extrudingthe molten resin through a spinning nozzle, subjecting the extrusionproduct to a high-temperature air stream to produce the extrusionproduct into a fibrous form while scattering the fibers, spraying thefibers on the surface of a conveyor or a collector such as anothernonwoven fabric to accumulate thereon, and then solidifying the fibers.

Since the meltblown nonwoven fabric is produced by accumulating a heatedand melted resin having fibrous form before the resin is completelysolidified, the meltblown nonwoven fabric has a feature that fibers areadhered in many parts. Therefore, the meltblown nonwoven fabric hasrelatively high modulus, and even if the nonwoven fabric is subjected toexternal force and is temporarily deformed, the nonwoven fabric caneasily restore its original shape upon releasing the external force.

Meanwhile, the softening point of the fibers constituting the meltblownnonwoven fabric of the second layer is preferably made lower than thesoftening point of the fibers constituting the spunbonded nonwovenfabric of the first layer. Then, on the occasion of producing theextraction filter and the like using the sheet material for extractionof the present embodiment, for example, when two sheets of the sheetmaterial for extraction are arranged such that the second layers of therespective sheets face each other, and the two sheets are adhered atpredetermined sites and subjected to a sealing treatment, the meltblownnonwoven fabric of the second layer having a low softening point ismelted and caused to function as an adhesive material. Further, thesheets of the sheet material for extraction can be subjected to asealing treatment while retaining the form of the sheet material forextraction, without softening the spunbonded nonwoven fabric of thefirst layer having a high softening point.

Particularly, when the difference between the softening point of thefibers constituting the spunbonded nonwoven fabric of the first layerand the softening point of the fibers constituting the meltblownnonwoven fabric of the second layer is adjusted to be as large as 30° C.or greater, and more preferably 40° C. or greater, the meltblownnonwoven fabric can be heated to a temperature significantly higher thanthe softening point thereof at the time of the sealing treatment,thereby melting the meltblown nonwoven fabric in a very short period oftime. Therefore, the time taken for the sealing treatment can beshortened, and furthermore, the time for producing the extraction filterand the like can be shortened. Thus, the production efficiency can beincreased.

Furthermore, when the meltblown nonwoven fabric of the second layer ismelted at high temperature, the resin can be sufficiently fluidized, andfor example, such a molten resin can be caused to infiltrate deeply intothe fiber spacings in the spunbonded nonwoven fabric by the compressionforce exerted by a sealing bar. Therefore, an anchor effect is produced,and high seal strength can be obtained.

Meanwhile, any known sealing treatment method such as adhesion by a heatsealing bar or adhesion by ultrasonic vibration can be widely appliedfor the sheet material for extraction of the present embodiment.

In order to regulate the softening point of the spunbonded nonwovenfabric of the first layer, the spinning speed may be regulated asappropriate at the time of spinning the constituent fibers. Furthermore,the softening point can also be regulated by mixing raw material resinshaving different molecular weights as appropriate, or adding variousadditives.

Furthermore, in order to regulate the softening point of the meltblownnonwoven fabric of the second layer, the heating temperature for meltingthe raw material polyester-based resin fibers may be regulated asappropriate at the time of spinning the constituent, or the temperatureof the air stream applied to the molten resin having fibrous form may beregulated as appropriate. Furthermore, the softening point can also beregulated by mixing raw material resins having different molecularweights as appropriate, or adding various additives.

The meltblown nonwoven fabric of the second layer has an average fiberdiameter of 16 to 28 μm. When the average fiber diameter is larger than28 μm, the fiber length per unit area becomes short in the meltblownnonwoven fabric, the fiber spacings become excessively wide, powderleakage is likely to occur easily, and thus production of the meltblownnonwoven fabric tends to become difficult. Further, when the averagefiber diameter is smaller than 16 μm, the fiber length per unit areabecomes long in the spunbonded nonwoven fabric, the fiber spacingsbecome excessively narrow, and transparency and extraction propertiestend to deteriorate.

The meltblown nonwoven fabric that forms the second layer has a basisweight of 2 to 8 g/m². When the basis weight is more than 8 g/m², thefiber length per unit area becomes long in the meltblown nonwovenfabric, the fiber spacings become excessively narrow, and transparencyand extraction properties tend to deteriorate. Further, when the basisweight is less than 2 g/m², since the fiber length per unit area becomesshort in the meltblown nonwoven fabric, the modulus is decreased, andthere is a tendency that the sheet material for extraction is likely tobe permanently deformed by external force.

Meanwhile, in the meltblown nonwoven fabric that forms the second layer,a nonwoven fabric other than the meltblown nonwoven fabric, e.g., anonwoven fabric produced by another spinning method, or another materialcan be incorporated to the extent without impairing the effects of theinvention. The mixing ratio of such other nonwoven fabric or the like ispreferably approximately 10% or less with respect to the meltblownnonwoven fabric.

Next, a method for laminating the first layer and the second layer ofthe sheet material for extraction of the present embodiment will bedescribed.

First, the first layer comprising the spunbonded nonwoven fabric isformed according to the spun-bonding method. This spunbonded nonwovenfabric may be in a web form in which spun fibers are merely accumulated,or may be a product of partial thermal compression treatment obtained bypassing the web between heated embossed rolls or the like.

Next, the second layer comprising the meltblown nonwoven fabric can beformed on the surface of this first layer by spraying, accumulating, andsolidifying a fibrous molten resin at a high temperature according tothe meltblown method.

At that time, when the softening point of the resin that forms themeltblown nonwoven fabric is made lower than the softening point of theresin that forms the spunbonded nonwoven fabric, the resin of themeltblown nonwoven fabric can be melted at a high temperature to theextent that the resin of the spunbonded nonwoven fabric is not softened.Therefore, even in a case where a fibrous molten resin is sprayed at ahigh temperature on the surface of the spunbonded nonwoven fabricaccording to the meltblown method, the meltblown nonwoven fabric can beformed on the surface of the spunbonded nonwoven fabric withoutdeforming the spunbonded nonwoven fabric, and can adhere the spunbondednonwoven fabrics.

Furthermore, by such a lamination method, the fibers of the meltblownnonwoven fabric infiltrate into the fiber spacings of the spunbondednonwoven fabric and then are solidified. Therefore, the so-called anchoreffect is produced, and the two nonwoven fabrics can be stronglyadhered, which is therefore preferable.

As to the sheet material laminated and formed as such, the thickness maybe adjusted by applying a pressing force over the entire surface usingthe flat roll as necessary, or may be subjected to the partial thermalcompression treatment using the embossed roll.

Furthermore, when a process forming the spunbonded nonwoven fabric and aprocess forming the meltblown nonwoven fabric are carried outsuccessively in a so-called in-line mode, the production efficiency canbe increased, which is therefore preferable.

Besides, regarding another method for laminating the first layer and thesecond layer, the spunbonded nonwoven fabric and the meltblown nonwovenfabric may be separately produced and then be superposed, this assemblymay be subjected to the partial thermal compression treatment using theembossed roll or the like, and thus the two nonwoven fabrics may beintegrated.

Meanwhile, the sheet material for extraction of the invention can beproduced into the sheet for extraction comprising three or more layersby further laminating another nonwoven fabric, a woven fabric, or thelike, to the extent without impairing the effects of the invention.

The sheet material for extraction of the present embodiment obtained bythe lamination method described above is such that the sum of thelengths of all fibers included in 1 cm² (hereinafter, referred to as“total fiber length”) is 3.3 to 4.8 m. In a case where the sheetmaterial for extraction is composed of two layers of the first layer andthe second layer only, the total fiber length is adjusted to 3.3 to 4.8m by summing the lengths of fibers included in 1 cm² of the spunbondednonwoven fabric forming the first layer and the lengths of fibersincluded in 1 cm² of the meltblown nonwoven fabric frming the secondlayer.

When the total fiber length is 3.3 to 4.8 m in the sheet material forextraction, the sheet material for extraction can simultaneously solvecontradictory problems of the enhancement of transparency and extractionproperties, and the reduction of powder leakage.

For example, as to the sheet material for extraction composed of thefirst layer and the second layer described above, provided that thetotal fiber length of the fibers constituting the two layers isregulated to the predetermined range, as the length of the fibersconstituting the first layer is lengthened to narrow the fiber spacing,the length of the fibers constituting the second layer becomesrelatively shorter, and the fiber spacing becomes wide. In contrast,when the length of the fibers constituting the first layer is shortenedto widen the fiber spacing, the length of the fibers constituting thesecond layer becomes relatively longer, and the fiber spacing becomesnarrow. Therefore, the fiber spacings come into a moderatelywell-balanced state over the entirety of the sheet material forextraction, thereby obtaining the sheet material for extraction havingexcellent transparency and extraction properties and less likely tocause powder leakage.

In this case, the transparency is preferably 40% or higher in the sheetfor extraction. Furthermore, the quantity of airflow, which serves as anindicator for extraction properties, is preferably 400 cc/cm³/sec orhigher. Moreover, the powder leakage rate is preferably 10% or less.

In a case where the total fiber length is more than 4.8 m in the sheetmaterial for extraction, the fiber spacings of the nonwoven fabricconstituting the sheet material for extraction becomes excessivelynarrow, and transparency and extraction properties are deteriorated.Further, in a case where the total fiber length is shorter than 3.3 m inthe sheet material for extraction, the fiber spacings of the nonwovenfabric constituting the sheet material for extraction become excessivelywide, and powder leakage easily occurs.

As to the sheet material for extraction of the present embodiment, the3% modulus needs to be adjusted to 5.5 N or greater, and more preferablyto 6.0 N or greater.

Generally, since fibers constituting the nonwoven fabric are adhered atmany parts in the meltblown nonwoven fabric, the movable range of therespective fibers tends to be limited. On the other hand, the spunbondednonwoven fabric has high tensile strength and is sturdy; however, sincethere are fewer adhered parts between the fibers, the movable range ofthe respective fibers tends to become wide. Such tendency isparticularly noticeably exhibited in a case where the basis weight issmall as in the present embodiment.

Since the sheet material for extraction of the present embodiment hasthe meltblown nonwoven fabric and the spunbonded nonwoven fabriclaminated together, the fibers of the spunbonded nonwoven fabric havingfewer adhered parts are connected to the meltblown nonwoven fabrichaving many adhered parts. Therefore, this sheet material for extractionis sturdy as a whole, and since the movable range of the respectivefibers is narrow, consequently the modulus can be made high.

In order to further increase the modulus of the sheet material forextraction, for example, it is desirable to increase the basis weight ofthe meltblown nonwoven fabric of the second layer. In order to increasethe 3% modulus to be 5.5 N or greater, it is preferable to adjust thebasis weight of the meltblown nonwoven fabric of the second layer to be2 g/m² or higher. In order to increase the 3% modulus to be 6.0 N orgreater, it is preferable to adjust the basis weight of the second layerto be 4 g/m² or higher.

However, depending on the state of the spunbonded nonwoven fabric of thefirst layer, even when the basis weight of the second layer is adjustedto be 2 g/m² or higher, the 3% modulus may become smaller than 5.5 N inthe sheet material for extraction. Therefore, the average fiberdiameter, the basis weight, and the like of the spunbonded nonwovenfabric of the first layer may be regulated in consideration of thispoint of view.

Since the sheet material for extraction of the present embodiment hasits 3% modulus adjusted to be 5.5 N or greater, the sheet material forextraction can easily restore its original shape, even when the sheetmaterial for extraction is subjected to external force and istemporarily deformed. For example, even when the sheet material forextraction is instantaneously subjected to a large tensile force andtemporarily undergoes deformation such as stretching upon the initiationof machine operation or emergency shutdown while the extraction filterand the like are produced using the sheet material for extraction, thesheet material for extraction immediately restores its original shape,and damage or permanent deformation cannot easily occur.

Therefore, regarding the sheet material for extraction of the presentembodiment, defective products and the like cannot be easily produced ina case where the sheet material for extraction is processed using themachine, and the sheet material for extraction has high machineadaptability.

Next, the embodiment of an extraction filter produced using the sheetmaterial for extraction of the invention will be described on the basisof FIG. 1.

An extraction filter 1 is a drip coffee filter mounted on and used in afunnel-shaped dripper (not illustrated in the drawing), and planarlyadhered portions 3 are provided at the bottom side and a lateral side ofan approximately inverted trapezoidal-shaped filter portion 2, with thesecond layers of the sheet material for extraction being disposed on theinner side. At the time of use, an upper edge 4 is opened, the filter isshaped into a mortar shape, powdered coffee is inserted through theopened upper edge 4, hot water is applied thereto from the above to befiltered, and thus a coffee beverage is extracted.

In order to produce the extraction filter 1, for example, the extractionfilter 1 may be produced by using a continuous long-shaped sheetmaterial for extraction as an original fabric, cutting out the sheetmaterial for extraction into a predetermined shape using a known shapingmachine, and planarly adhering the sheet material for extraction.

Meanwhile, the adhesion method other than planar adhesion can beemployed such as adhesion by ultrasonic vibration, oradhesion-cutting-sealing of performing cutting and adhesion of the sheetfor extraction simultaneously.

The extraction filter 1 produced as such has superior extractionproperties for coffee beverage and exhibits reduced powder leakage.

Meanwhile, the shape of the extraction filter 1 is not limited to theapproximately inverted trapezoidal shape illustrated in FIG. 1, and canbe produced into an arbitrary shape such as an approximately invertedtriangular shape or a disc shape. Furthermore, there are no particularlimitations on the size or the method of use.

Next, the embodiment of an extraction bag produced using the sheetmaterial for extraction of the invention will be described on the basisof FIG. 2.

An extraction bag 5 is a product that is generally called teabag, andcomprises a bag body 6 formed into a tetra-form (tetrahedral form) usingthe above-described sheet material for extraction; a tag 9 for pickingup the extraction bag 5 with fingertips when the extraction bag 5 isused; and a tagging thread 8 having one end adhered to the upper end ofthe bag body 6 and the other end adhered to the tag 9. The bag body 6 isformed into a bag shape by disposing the second layers of the sheetmaterial for extraction on the inner side, and forming a linear adheredportion 7 along the edge portion of the respective sides by ultrasonicvibration, and dried tea leaves for green tea as the extraction material(not illustrated in the drawing) are encapsulated in the inside of thebag body.

In the case of using such an extraction bag 5, for example, the tag 9may be held with fingertips, the bag body 6 may be immersed into a cupcontaining hot water for a time of from several seconds to severalminutes, and then the dried tea leaves inside the bag body 6 may beinfused with hot water to elute green tea components.

Regarding the method for forming the bag body 6, for example, the bagbody 6 may be formed from the above-described sheet material forextraction having a continuous long shape as the original fabric bycutting and linearly adhering the sheet material for extraction using aknown shaping and filling machine while dried tea leaves is filled andsealed therein. At that time, linear adhesion of the bag body 6 can beperformed by applying vibration to the adhesion-intended sites of thesheet material for extraction using ultrasonic waves and increasing itstemperature.

Meanwhile, other adhesion method can be employed such as planar adhesionbased on pinching with a heat sealing bar and adhesion-cutting-sealingof simultaneously performing cutting and adhesion of the sheet forextraction and the like.

The bag body 6 thus formed has excellent transparency, and the beautifulgreen color of the tea leaves encapsulated inside the bag body 6 can besufficiently visually recognized from the outside. Furthermore, the bagbody 6 has high extraction properties for green tea and causes lesspowder leakage.

Meanwhile, the shape of the bag body 6 is not limited to the tetra-formillustrated in FIG. 2, and any arbitrary shape can be employed such as apillow shape, a pyramid shape, a disc shape, or a stick shape.Furthermore, there are no particular limitations on the size andcapacity of the bag body 6, and method of use. In addition, it is alsopossible to temporarily affix the tagging thread 8 and the tag 9 to thesurface of the bag body 6 with a force to the extent that can be easilypeeled off at the time of use.

The extraction bag 5 after production is preferably packaged per oneeach or a plurality of the bag bodies 6 in an external bag formed from aresin film, paper, or the like, which is not illustrated in the drawing,or in an external container, in order to maintain the flavor of the tealeaves inside the bag body 6 and to prevent contamination or damage.

EXAMPLES

Hereinafter, the invention will be specifically described by way ofExamples; however, the invention is not intended to be limited to theseExamples.

First, methods for measuring or testing various indicators according tothe invention will be described.

(1) Average Fiber Diameter (Unit: μm)

For the fibers of a nonwoven fabric as a test object, the diameters weremeasured at ten sites by visual inspection using an optical microscope,and the average value was determined.

(2) Basis Weight (Unit: g/m²)

A specimen that measured 10 cm on each of four sides was collected froma nonwoven fabric as a test object according to JIS L-1906, the mass wasmeasured, and the basis weight was calculated.

(3) Total Fiber Length (Sum of the Lengths of All Fibers Included In 1cm² of the Sheet Material for Extraction, Unit: m)

First, the sum I₁ (m) of the lengths of fibers of the nonwoven fabric ofthe first layer included in 1 cm² of the sheet material for extractionas a test object was calculated by the following formula from theaverage fiber diameter d₁ (μm) of the nonwoven fabric of the firstlayer, the basis weight w₁ (g/m²) of the nonwoven fabric of the firstlayer, and the density 1.38 g/cm³ of polyethylene terephthalate.

I ₁=(4×10² ×w ₁)/(1.38×π×d ₂ ²)

Next, the sum I₂ (m) of the lengths of fibers of the nonwoven fabric ofthe second layer included in 1 cm² of the sheet material for extractionas a test object was calculated by the following formula from theaverage fiber diameter d₂ (μm) of the nonwoven fabric of the secondlayer, the basis weight w₂ (g/m²) of the nonwoven fabric of the secondlayer, and the density 1.38 g/cm³ of polyethylene terephthalate.

I ₂=(4×10² ×w ₂)/(1.38×π×d ₂ ²)

The sum of I₁ and I₂ calculated as described above was determined, andthe sum was designated as the total fiber length.

(4) 3% Modulus (Unit: N)

A band-shaped specimen of the sheet material for extraction, whichmeasured 100 mm in the longitudinal direction and 15 mm in the widthdirection, was collected from a long-shaped sheet material forextraction as a test object. With this specimen, the tensile strength inthe longitudinal direction of the sheet material for extraction wasmeasured using a digital force gauge (manufactured by IMADA CO., LTD.,product name ZTA-50N) and a measuring stand (manufactured by IMADA CO.,LTD., product name MX2-500N) while the conditions were set to a lengthof specimen between grips of 50 mm and a speed of 100 mm/min. The loadat the time of 3% (1.5 mm) elongation was read out using an affiliateddriver software program, and this load was designated as the 3% modulus.

(5) Transparency (Unit: %)

A specimen collected from the sheet material for extraction as a testobject was irradiated with visible light (wavelength 380 to 780 nm), andthe proportion (%) of transmitted light to the light incident withrespect to the nonwoven fabric was measured using a spectrophotometer(manufactured by Hitachi High-Technologies Corporation, product nameU-3900H).

(6) Quantity of Airflow (Unit: cc/cm³/sec)

A specimen collected from the sheet material for extraction as a testobject was mounted on an attachment having a diameter of 36 mm using anair permeability testing machine (manufactured by YASUDA SEIKISEISAKUSHO, LTD.), and the quantity of airflow was measured by themethod according to Frazier method (JIS-L-1906).

(7) Powder Leakage Rate (Unit: %)

A specimen collected from the sheet material for extraction as a testobject was mounted on a screen frame having a diameter of 7.2 cm, andabout 10 g of glass beads BZ-04 (particle size 350 to 500 μm, handled byAS-ONE Corporation) weighed up to the digit of 0.001 g were rested onthe above-described nonwoven fabric and were shaken for 14 minutes at aspeed of vibration of 213 rpm using a shaking tester (manufactured byIKA Japan, product name Digital Shaker HS501). Then, glass beads thathad passed through the nonwoven fabric were weighed up to the digit of0.001 g.

The weighed mass of glass beads before screening was designated as W1(g), and the weighed mass of glass beads that had passed through thenonwoven fabric was designated as W2 (g). Thus, the powder leakage ratewas calculated by the following formula.

Powder leakage rate (%)=(W2/W1)×100

Example 1 Sheet Material for Extraction

Polyethylene terephthalate that had been heated and melted was extrudedthrough the spinning nozzle into a fibrous form, and the resin in thefibrous form was stretched at a spinning speed of 5,000 m/min using anejector while being cooled, to form long fibers. Those long fibers wereaccumulated on the belt conveyor that moved at a constant speed, andthus the spunbonded nonwoven fabric (first layer) was formed.

Next, a polyester (the polymerization ratio of terephthalicacid/isophthalic acid in acid components is 86/14) that had been heatedand melted was extruded through the spinning nozzle into a fibrous form,and the resin in the fibrous form was subjected to an air stream heatedto 370° C. and was scattered. The resin in a fibrous form was sprayed,accumulated, and solidified on the surface of the spunbonded nonwovenfabric that moved at a constant speed, and the meltblown nonwoven fabric(second layer) was formed thereon. At the same time, the two nonwovenfabrics were adhered, subsequently the thickness was adjusted to 80 μmby passing the adhered nonwoven fabrics through between flat rolls, andthus the long-shaped sheet material for extraction was produced.

With regard to the sheet material for extraction thus obtained, theaverage fiber diameter of the spunbonded nonwoven fabric that formed thefirst layer was 21 and the basis weight was 16 g/m². Besides, theaverage fiber diameter of the meltblown nonwoven fabric that formed thesecond layer was 18 and the basis weight was 4 g/m².

Furthermore, with regard to this sheet material for extraction, the sumof the lengths of all fibers (total fiber length) included in 1 cm² was4.49 m in the sheet material for extraction, the 3% modulus was 6.3 N,transparency was 43.1%, the quantity of airflow was 445 cc/cm³/sec, andthe powder leakage rate was 7.5%.

Example 2 Extraction Bag Illustrated In FIG. 2

The long-shaped sheet material for extraction of Example 1 describedabove was mounted on the shaping and filling machine, and thetetra-shaped bag body 6 was formed by linearly adhering predeterminedsites by ultrasonically vibrating the sheet material for extractionwhile dried tea leaves of green tea were encapsulated therein. Thus, theextraction bag 5 was produced.

During the production of the extraction bag 5, partial deformation suchas stretching of the sheet material for extraction did not occur,thereby avoiding the generation of defective products caused bydeformation of the sheet material for extraction.

Furthermore, the extraction bag 5 thus produced was such that 2 g ofdried tea leaves were encapsulated in the tetra-shaped bag body 6 havingeach side length of 55 mm and having linearly adhered portions 7 formedalong the edge of the respective sides. Thus, the dried tea leavesinside the bag body 6 were clearly visible through the sheet materialfor extraction that formed the bag body 6, and the green color of thetea leaves was felt beautiful.

Furthermore, this extraction bag 5 was immersed into hot water at about95° C. for 1 minute, and during the time, the extraction bag wasreciprocatingly shaken about 10 times to produce green tea. Hot waterinfusion of the dried tea leaves could extract green tea to asatisfactory concentration quickly in a short time period, and thenpowder leakage almost failed to occur.

Test Example

Samples a to t of twenty kinds of sheet material for extraction wereproduced as shown in the following Table 1 and Table 2. The samples thusobtained were measured for the average fiber diameter and basis weightof the nonwoven fabric in the first layer, and the average fiberdiameter and the basis weight in the second layer, and further the totalfiber length, 3% modulus, transparency, quantity of airflow, and powderleakage rate in the sheet material for extraction. The results arepresented in Table 1 and Table 2.

Meanwhile, samples a to i shown in Table 1 are “samples of Examples”that satisfy the requirements of the invention, and samples j to t shownin Table 2 are “samples of Comparative Examples” that do not satisfy therequirements of the invention.

The methods for producing the respective samples are as follows.

Sample a: This sample is an equivalent product produced by the samemethod as the sheet material for extraction of Example 1 describedabove.

Samples b, q, and r: The spinning speed by the ejector and the speed ofmovement of the belt conveyor were changed as appropriate while formingthe spunbonded nonwoven fabric of the first layer in the production ofthe sheet for extraction of Example 1. Other conditions of manufacturewere the same manner as that of Example 1.

Samples d, e, g, k, and n: The heating temperature for melting the rawmaterial polyester, the temperature of the air stream applied to themolten resin extruded through the spinning nozzle, and the speed ofmovement of the spunbonded nonwoven fabric of the first layer werechanged as appropriate while forming the meltblown nonwoven fabric ofthe second layer in the production of the sheet for extraction ofExample 1. Other conditions of manufacture were the same manner as thatof Example 1.

Samples c, f, h, i, j, l, m, o, and p: The spinning speed by the ejectorand the speed of movement of the belt conveyor were changed asappropriate while forming the spunbonded nonwoven fabric of the firstlayer in the production of the sheet for extraction of Example 1.Further, the heating temperature for melting the raw material polyester,the temperature of the air stream applied to the molten resin extrudedthrough the spinning nozzle, and the speed of movement of the spunbondednonwoven fabric of the first layer were changed as appropriate whileforming the meltblown nonwoven fabric of the second layer. Otherconditions of manufacture were the same manner as that of Example 1.

Samples s and t: The spinning speed by the ejector and the speed ofmovement of the belt conveyor were changed as appropriate while formingthe spunbonded nonwoven fabric of the first layer in the production ofthe sheet for extraction of Example 1. The meltblown nonwoven fabric ofthe second layer was not laminated, and other conditions of manufacturewas the same manner as that of Example 1.

TABLE 1 Sample a b c d e f g h i Sheet Material Total Fiber Length 4.493.31 3.61 4.79 4.07 4.26 4.29 3.89 3.42 for Extraction (m/cm²) BasisWeight 20 16 22 20 18 14 24 12 23 (g/m²) 3% Modulus 6.3 5.8 7.1 6.2 5.55.6 6.8 5.5 7.4 (N) Transparency 43.1 52.1 48.6 41.7 46.1 42.1 41.5 48.645.3 (%) Quantity of Aiflow 445 662 551 429 480 435 402 485 521(cc/cm³/sec) Powder Leakage 7.5 8.44 9.02 3.51 8.1 7.92 4.02 9.53 8.14Rate (%) First Layer Average Fiber 21 22.6 27.7 21 21 18.1 21 18.1 27.7Diameter (μm) Basis Weight 16 12 18 16 16 10 16 8 19 (g/m²) Second LayerAverage Fiber 18 18 16 16 16 16 28 16 16 Diameter (μm) Basis Weight 4 44 4 2 4 8 4 4 (g/m²)

From Table 1 described above, the following matters can be understood.

In a case where the average fiber diameter is 18 to 28 μm in thespunbonded nonwoven fabric of the first layer of the sheet material forextraction, the basis weight is 8 to 19 g/m² therein, the average fiberdiameter is 16 to 28 μm in the meltblown nonwoven fabric of the secondlayer, the basis weight is 2 to 8 g/m² therein, and the total fiberlength is 3.3 to 4.8 m in the sheet material for extraction, the 3%modulus is 5.5 N or higher in the sheet material for extraction,transparency is 40% or higher, the quantity of airflow is 400 cc/cm³/secor greater, and the powder leakage rate is 10% or less (samples a to iof Examples).

TABLE 2 Sample j k l m n o p q r s t Sheet Material Total Fiber Length4.86 3.85 3.02 3.17 4.82 4.95 3.18 3.1 4.91 3.27 3.21 for Extraction(m/cm²) Basis Weight 15 17.4 13.4 17.4 28.5 22 22 16 22 12 15.5 (g/m²)3% Modulus 7.2 4.7 4.5 4.5 7.1 7.6 6.4 5.6 6.5 5.1 5.3 (N) Transparency38.8 47.2 49.1 48.4 39.1 37.1 50.1 52.9 39.2 47.5 48.1 (%) Quantity ofAiflow 410 499 621 589 360 437 580 680 401 685 691 (cc/cm³/sec) PowderLeakage 4.62 8.9 12.5 10.8 2.15 4.52 13.5 11.5 3.07 8.9 9.52 Rate (%)First Layer Average Fiber 17.2 21 21 23.5 21 27.7 29.2 23.8 21 18.4 21Diameter (μm) Basis Weight 11 16 12 16 16 18 16 12 18 12 15.5 (g/m²)Second Layer Average Fiber 16 16 16 16 28 11.5 16 18 18 — — Diameter(μm) Basis Weight 4 1.4 1.4 1 .4 12.5 4 4 4 4 — — (g/m²)

From Table 2 described above, the following matters can be understood.

When the average fiber diameter is more than 28 um in the spunbondednonwoven fabric of the first layer, the powder leakage rate is more than10% in the sheet material for extraction, and thus powder leakage islikely to occur (sample p of Comparative Examples).

When the average fiber diameter is smaller than 18 um in the spunbondednonwoven fabric of the first layer, transparency is decreased andbecomes less than 40% in the sheet material for extraction (sample j ofComparative Examples).

When the average fiber diameter is smaller than 16 um in the meltblownnonwoven fabric of the second layer, transparency of the sheet materialfor extraction is decreased and becomes less than 40% (sample o ofComparative Examples).

When the basis weight is smaller than 2 g/m² in the meltblown nonwovenfabric of the second layer, the 3% modulus is decreased and becomes lessthan 5.5 N in the sheet material for extraction (samples k, 1, m, s, andt of Comparative Examples). Furthermore, the powder leakage rate exceeds10% in the sheet material for extraction, and powder leakage is likelyto occur (samples 1 and m of Comparative Examples).

When the basis weight is more than 8 g/m² in the meltblown nonwovenfabric of the second layer, transparency is decreased and becomes lessthan 40% in the sheet material for extraction. Furthermore, the quantityof airflow is decreased and becomes less than 400 cc/cm³/sec, and theextraction properties become insufficient (sample n of ComparativeExamples).

When the total fiber length is more than 4.8 m in the sheet material forextraction, transparency is decreased and becomes less than 40% in thesheet material for extraction (samples j, o, and r of ComparativeExamples).

When the total fiber length is shorter than 3.3 m in the sheet materialfor extraction, the powder leakage rate is more than 10% in the sheetmaterial for extraction, and powder leakage is likely to occur (samplesl, m, p, and q of Comparative Examples).

INDUSTRIAL APPLICABILITY

The sheet material for extraction, the extraction filter, and theextraction bag according to the invention have excellent transparencyand extraction properties and are less likely to cause powder leakage.Therefore, these can be suitably utilized in the fields of a sheet forextraction, an extraction filter, and an extraction bag, which are usedfor the extraction of beverages such as black tea, green tea, andcoffee; liquid food products such as soup; medicines such as Chineseherbal medicines; or quasi-drugs such as a bathing agent.

REFERENCE SIGNS LIST

1 extraction filter

2 filter portion

3 planarly adhered portion

4 upper edge

5 extraction bag

6 bag body

7 linearly adhered portion

8 tagging thread

9 tag

1. A sheet material for extraction comprising: a first layer including aspunbonded nonwoven fabric formed from polyester-based fibers having anaverage fiber diameter of 18 to 28 μm and a basis weight of 8 to 19g/m²; and a second layer including a meltblown nonwoven fabric formedfrom polyester-based fibers having an average fiber diameter of 16 to 28μm and a basis weight of 2 to 8 g/m², wherein the sheet material forextraction has a sum of the lengths of all fibers included in 1 cm² ofthe sheet material for extraction of 3.3 to 4.8 m and a 3% modulus of5.5 N or higher.
 2. The sheet material for extraction according to claim1, wherein the sheet material for extraction has a transparency of 40%or higher, a quantity of airflow of 400 cc/cm³/sec or greater, and apowder leakage rate of 10% or less.
 3. An extraction filter comprisingthe sheet material for extraction according to claim 1, wherein theextraction filter is formed by superposing the sheet material forextraction with the second layer being disposed on the inner side, andadhering the sheet material for extraction at predetermined sites.
 4. Anextraction bag comprising the sheet material for extraction according toclaim 1, wherein the extraction bag is formed by superposing the sheetmaterial for extraction with the second layer being disposed on theinner side, and adhering the sheet material for extraction atpredetermined sites to form a bag body with which an extraction materialhas been filled.
 5. An extraction filter comprising the sheet materialfor extraction according to claim 2, wherein the extraction filter isformed by superposing the sheet material for extraction with the secondlayer being disposed on the inner side, and adhering the sheet materialfor extraction at predetermined sites.
 6. An extraction bag comprisingthe sheet material for extraction according to claim 2, wherein theextraction bag is formed by superposing the sheet material forextraction with the second layer being disposed on the inner side, andadhering the sheet material for extraction at predetermined sites toform a bag body with which an extraction material has been filled.